Major effort has been put in recent years on the development of Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) in order to achieve higher data rates and system capacity. In 3GPP LTE-Advanced (LTE-A) cellular systems, device-to-device (D2D) communication has been proposed to enable the proximity-based service. The D2D communication allows user equipment (UEs) to communicate with each other through a direct connection, operating in uplink (UL) spectrum in the case of Frequency Division Duplex (FDD) or UL subframes in the case of Time Division Duplex (TDD). In general, there are two modes for D2D communication resource allocation, Mode 1 and Mode 2. In Mode 1, a base station schedules exact resource for D2D UEs within its cell coverage to transmit control information and D2D data. In Mode 2, a D2D UE autonomously selects resource for D2D communication from a resource pool.
For D2D communication Mode 1, a D2D-grant signaling is transmitted by the base station in a downlink signaling channel to a D2D Transmit (Tx) UE for the purpose of indicating resource for D2D data communication and related control information. In particular, the control information, which can be also referred as scheduling assignment (SA), is used to indicate resource for reception of the associated D2D broadcasting data to the corresponding D2D Receive (Rx) UE(s). Additional necessary control information is also included in the SA, e.g., Modulation and Coding Scheme (MCS) for D2D data transmission, timing advance (TA), etc. The Tx UE may transmit the SA and associated broadcasting data to the Rx UE(s) after receiving the D2D-grant signaling, using the resource that is indicated in the D2D-grant signaling.